let obj = {
  age: 12,
  name: 'ling'
};

let freezeObj = Object.freeze(obj);

freezeObj.age = 13;
delete freezeObj.name;
freezeObj.schoolName = 'ling_ren'
console.log(freezeObj)

// let sealObj = Object.seal(obj);

// sealObj.age = 15;
// sealObj.schoolName = 'ling_ren'
// delete sealObj.name;
// console.log(sealObj)

// let extensionsObj = Object.preventExtensions(obj);

// extensionsObj.age = 14;
// extensionsObj.schoolName = 'ling_ren'
// delete extensionsObj.name;
// console.log(extensionsObj)
